In this project, we propose to investigate the storage and manipulation of quantum states in waveguide-based superconducting circuits that operate near 94 GHz, significantly higher than state-of-the-art few GHz superconducting circuits. At 94 GHz, the increase of hf/kB to roughly 5 K makes long-term scalability to very large systems more feasible. We develop millimeter-wave superconducting circuits based on waveguides produced by wafer-scale silicon processing. We develop new thin film processes for coating the waveguides with superconductors, with sputtered Nb or NbN. Further, for improved step coverage, the development of ALD NbN is considered. We develop high-Q cavity resonators for studying the available coherence times and loss mechanisms, especially considering how the density of so called two-level systems (TLS) changes with frequency in order to clarify their microscopic origin. Josephson parametric devices using the resonators will be designed.

2020

2024